A prior antenna apparatus mounted on a vehicle is generally an antenna apparatus capable of receiving AM broadcasting and FM broadcasting. A prior antenna apparatus uses a rod antenna of about 1 m in length to receive AM broadcasting and FM broadcasting. The length of the rod antenna corresponds to about ¼ wavelength in the FM wave band, but when compared with a wavelength in the AM wave band, the length thereof is far shorter and thus, sensitivity thereof declines dramatically. Therefore, a high-impedance cable has been used to increase the impedance of a rod antenna for the AM wave band or an amplifier in the AM wave band has been used to ensure sensitivity. Moreover, an on-vehicle antenna apparatus in which the length of antenna is reduced to about 180 mm to 400 mm by adopting a helically wound helical antenna for the rod part of the antenna is used. However, an amplifier is placed immediately below the antenna to compensate for performance degradation due to a reduced rod part.
FIG. 23 shows a configuration in which a prior antenna apparatus 101 whose rod part is made shorter is mounted on a vehicle 102. As shown in FIG. 23, the prior antenna apparatus 101 is mounted on the roof of the vehicle 102 and a height h10 of the antenna apparatus 101 sticking out from the vehicle 102 is set to about 200 mm. A helically wound helical antenna is adopted for the rod part of the antenna apparatus 101. Since, as described above, the antenna apparatus 101 sticks out from the vehicle 102, the rod part thereof may be broken by collision when the vehicle 102 is parked in a garage or washed. Thus, an antenna apparatus whose rod part can be pushed down to be in alignment with the roof of the vehicle 102 is also known.
Patent document 1: Japanese Publication Unexamined Patent Application No. 2005-223957
Patent document 2: Japanese Publication Unexamined Patent Application No. 2003-188619